Phantom circuit.



F. H. FAY, T. SHAW'& J. l. PILLIOD.

' PHANTOM cmcun.

APruc/mon man oci'. 1. m4. 1, Ptellted Feb. 29, 1916.

3 SHEETS-SHEET l.

Fig. 1.

Frane tom ay Thomas Shaw da mes el Iliad, y @BT-3mm 777017105 15 IV ,um f1, l J mesJPfz/i ad y M-"M tty.

Peeentea Feb. 29,1916.

F. H. FAY, T. SHAW & 1.*1. PILLIOD.

PHANTOM CIRCUIT.

APPLlcAnoN FILED 001.1. 1914.

I 2 Naf.. I

nfars Fay Thomas' ,S77 JamesJ Pillad and Illinois, respcctivel Eli@ Fnsi-isn. MAY, or Biase-Krimi, NEW "rossi, fs-ioivis siii-iw, or HACKENsAc, NEW` JERSEY, AND JAMES J. PILLD, QE" CHICGO TELEPHONE AND TELEGRAPH COEANY, A C

Application iled {Ictooer 7.

To ali @cli/,im iii' may concern e Be it known that 'Ti-ienne Sir-i f, and

oliirgen, and Jerseyi yhav inventedV cer tain' Improvements in santo which the following is a In telephone practice, in y phantom circuits, it may he found desirabie to change. the type of circuit from one which is properlyr organized to' prevent disturb ance to-cnev which tends to introduce noise induction frem-otherfcircuits and crosstaik between the phantfiis. i' n instance of this is where open w' Icircui...a are ied intr tral stations through non-duplex eahie'in 'which the sides-or the physical' circuits each phantom are carried by separate. pairs, instead of throiighduplex` cable having both pairs of the phantom assembled in a quad` cago, inthe counti Cool( and States of i" 'In such cases, ithas been customary to install the usual phantom repeating coils at the end of the open wire circuits and bring in the ihantciiis from that `point. by vmeansY ot'physical circuits furnished by` separate pairs in thel cable. By thisplan, .howeverlv the conductive Ycrntiiiuity l.ofl the" side-cir! cuits is interrupted at the repeating coils, and when it is desired t0 utilize the 'conductors for telegraph:operation the composite sets mustbeinstalled at the juncture of the open linesand the cable, and. the Morse legs carried to the central station liy separate conductors. Even in absence ofcomposite operation arrangements must be made for closing the circuits through to permit testing. and this requires the presence of relays associated witliv-lthephantcm repeating coils and conduct-ors inthe cable to control said relays. This placs apparatus where it is more troublescmeto maintain, and requires the presence of added conductors in the cable. This invention overcomes these dithculties by furnishing` direct current paths through the repeating coils or otheipham. tcmforming devices, tlie--eleii'ients being so arranged that phantom circuit imbalance and phantom to phantom crosstall: in the nensduplex cable is prevented. At the same time, the means for effecting` these ends may be so organized as to reduce rei'iection losses in the phantOm circuit, if the phen-.tain

Specification o: Letters Patent.

`H\I'GIS, ASSIGNORS TO AMERCAN QEIA'ION OF YORK'.

Patented Feb. 29, 1916.

scrai No. 395542.

"ier .audits ihjfsical extension are of difimpedance.

ie ac-conipanying drawings, in which ference characters are applied to simi# parts throughout, Figure l illustrates lthe infvention diagramniatically in itsapplication" to the 'sections of a phantom circuit in which the impedance is to be stepped up; Sig'. 2 shows the theory of this organization by a .Simplified diagram; 'F-ig. 3 is a' dia I' grammatic representation of ari-autotranstoriner employed in the system of Figsyl and 25; and Figs. 4, 5 and (3 correspond to Figs. l, 2 and 3, respectii'ely, illustratingan arrangement for producing a stepping down j of the phantom in'ipedance.

ii/ligyl ot the drawings appear telephone lines L and L, which may be of open wire and loadeth they being continued from the point A, say at the outskirts of a city', to l a central station B by non-duplexieable extensionsl and Z2, also loaded. To -eaich line may be4 connected telephone apparatus Composite sets t provide for telegraph transmission over each of the conductors ot' the open wire line and its cableextenson, the customary7 telegraph apparatus being contained in theh selegs Tlfoftlie circuits.

',Ioailow thel fo'iiination` ot the' pliantonLde-'- vices are located at the iiinc'tion A between each of the lines L, L2 and their extensions Z ,Zi'these devices in the present instance consisting o f the well known phantom lrepeating coils Rand R2, having line windv ings fw, 'zo and extension or drrp windings w', 'w'. These operate as usual to yinduc- 'tiveiy convey freni one section to the other voice currents flowing through the conductors of the side circuits in series, and tofi'irnish peints 10 between the windings w, w,

neutral with respect to such side current. to y which the physical extension pof the plian tom lmay be joined to conduct voice currents passing through each of the pairs of con;

doctors of the lines L' and Lgrin parallel."

To the extensiony p may be ccnncctedtelephone apparatus S.' In this instance the impedance of the extension 77 is assumed to' be greater thanthat of the open u'iiephantom, as would be the case if the phantom extension were loaded 'to approximate the impedance of the side circuitsL and Lf.

Since the phantom repcating'ccils open t; e sections of the conductors L, L2 and l, l?

" tensions.

to direct current, means are provided for conductively associating each of these, such means being preferably furnished by windings of autotransformers I, I2 which also serve to step up the impedance of the phantom to that of its extension. To enable these devices to perform their plural functions, the windings of each are included in the circuits in a manner which may\ bemore clearly understood by considering the simplified `diagram of Fig. 2 in ,connection with Fig. 1. In Fig. 2 light lines represent single con ductors, while :those lcorresponding to two conductors in -parallel are heavy. WVindings wz, w3, of each autotransformer, which, for reasons which will later more clearly appear, are termed bridge windings, unite points 11, 12 and 13, 14, respectively, at the inner extremities of the windings w and w of the phantom repeating coils R, R2. These furnish independent paths for telegraph or other direct currents in each of theV conductors of the side circuits and their ex- Bridged across the points 11 and 13 are balanced condensers c, c, between which the connections 10 for the conductors of the phantom extension p are made. In each of'said phantom extension conductors is a series winding w* of the autotransformcr. Ina bridge between the points 12 and 14 at the inner ends of the drop windings fw, w', of each phantom repeating coil is another pair of balanced condensers c', c', and at neutral points 15 at the center of each is joined a conductor I) completing a shortcircuiting bridge. Referring particularly to Fig. 2, it will be seen that the windings 'wz and 'w3 ofthe autotransformers I and I2, with the condensers c and the connection b, are in a bridge of the phantom at the juncture of the low and high impedance sections, while the windings fw are in series with the phvsical extension ofthe phantom. The

reflection reducing effect of the transformers equals the ratio of the impedance of the series windings fw* inductively associated with the bridge windings 1112, w3 in parallel-seriesaiding to the impedance of said bridge windings in parallel series ,aiding.v Obviously, this relation may be varied. to meet the particular conditions encountered. The

autotransformers cause transmission losses in the phantom circuit proportionate to their self and mutual impedances; these may be made small. With respect to the side circuits, the bridge windings 102, w3: are in series-opposing, and as they are included in said side circuits close to neutral points,

practically none of the current in these cir-l cuits flows through them and the transmis-4 sion losses are slight. Sincethe series windings fw* are entirely removed from side circuits they have no effectthereon.

Naturally a conductive connection between the lines L, L2, which carry phantom curformer windings.

, rent and the side' circuit extensions Z, Z2 makes possible an unbalance of the phantom and noise lndu'ction, if one of these side circuit extensions be switched to a line having greater admittance to ground than the line to which the other side circuit extension may be united, because more phantom current will pass to ground through one of the connected lines than through the other. But with this invention the terminal conditions of the side circuit extensions are practically without infiuence on the phantom, because of the conductive association of lthe side cir-` cuit extensions with the-phantom atsubs'tantially neutral points 12 and 1 4 therein', located in a bridge consisting of; autotransormer windings wz, w zcondense`rs-c and the conductor b, the impedancesoftheI condensers being low in comparison withthat of the wind-ings in parallel-seriesjaiding.

This circuit arrangement reduces tol a negligible minimum any induced potentials to ground acting on the diverse admittancesftof" ground of the side circuit terminal extensions. The conductive relations between the phantom lines and the non-duplex side circuit extensions also'tend to promotefnoiseabove character are practically eliminated by substantially excluding the phantom cur- A rent from the side circuit extensions; and the noise troubles are minimized by preventing noise induction picked -up by` the sidecircuit extensions, actingas an unbalanced element of the phantom, from being transferred to the balanced port-ion of the phantom. These results are accomplished bythe peculiar arrangement of the phantom interference preventing bridge previously referred to, in -which the autotransformer bridge windings w2, w3by virtue of their impedance, oppose the 'transfer of crosstalk and noise currents between the balanced and unbalanced elements of thephantom circuit and vice versa, whilesimultaneously assisting in the establishment of the iis conductive through-circuit required for Y Morse or testingpurposes, and the condens'- ers c lin conjunction with the short-circuit act as a low impedance shunt across the series path of the disturbing currents, which includes the high impedance autotransbetween the Morse legs is avoided by the presence of the condensers c and o' in the Conductive interference phantomconnecting and short-circuiting bridges, the capacity of these being small enough to prevent cross lire yet sufficiently large to give good telephonie transmission.

In the previous description the devices I and I2 have been referred to as having distinct functions in connection with the two side circuits, and while they could in fact be independent, for the sake of obtaining more perfect balance their windings are preferably placed upon a common core. Such an arrangement is illustrated in Fig. 3 of the drawings. The windings for each side circuit are placed on opposite halves of the usual toroidal core 1'. The bridge windings 102,103 are preferably in the form of a twisted pair extending uniformly about each half core. r1`his gives the best balance and is convenient in manufacture, while the increased capacity effect between the conductors is not objectionable, on account of their practical freedom from side circuit current. The series winding w* is carried outside the corresponding bridge windings about the half core. Considered with regard to the phantom current the windings of the autotransformers I and I3 are distributed evenly about the entire core, preventing leakage losses. Such a coil for stepping up the impedance of the lline phantom to that of the phantom extension in the ratio of 12400 to 1800 might have the following windings: Each bridge winding wz or w3 in either coil I or I2 has 139Q'turns of No. 26B. and S. gage single cotton-covered copper wire, having a directcurrent resistance of 44.1'ohms and impedance values together in series-parallelaid ing to phantom current of 800 periods per second of 5400 ohms resistance and 7 henries in'ductance; each series winding '104, 187

turns No. 16 B. Vand S. gage single cotton-v covered copper wire, direct current resistance 0.7 of an ohm, impedance t( gether in seriesaiding 99 ohms and 0.13 of a henry. The mutual impedance between the bridge and 'series groups would be 730 ohms and 0.95 -of a henry. The condensers aand c of this system would have capacities of about two microfarads each. Q

Sometimes the'phantom circuit extension maybe of lowerjimpedancey than the line portion, as in theeas of terminating a loaded operifwile irnoni-'loa'ded physical cable circuit. Hereit isfriecessay to so locate thesfis Widiigsfthat their im pedan ce is appliedtbitli ilie portion of the phantom;th atfifjtiit they are in direct conductive relatief; Withthfe line wires of the circuits.AVV Sll'iy tiri arrangement appears in Figs. 4 andf bfjth drawings. The circuits L, Z, L", lgfaiid 'p antlgiwtleahantom `repeating coils It andR2 areas before.' .PS0 too are the bridge windings w2 and w3 of the a utotran'sformers I andlandthe shorteoiiwitingbridge c b o', but there'isa sentes'windtngifw5 or we fw fzi'no for each of the side circuit conductors from points 16 and 17 at the inner ends of the line windings of the phantom repeating coils to points 18, 19, respectively, at the inner extremities of the bridge windings w?, w3. The condenser bridges providing the neutral connections 10, 10 for the phantom extension p are taken from the last named points 18 and 19. The reflection-reducing efficiency of this arrangement will be measured by the impedance ratio of the parallelseriesaiding grouping of the series windings w, co6 indu'ctively associated with the parallel-seriesaiding grouping of the bridge winding to the impedance of the parallel-series-aiding grouping of the bridge windings wg, The paths for the conduction of direct current are through the series and bridge wind ings w, 102 and we, in series. The general considerations governing the operation of this system are similar to those of Figs. 1 and 2. A bridge containing a condenser c2 is preferably placed across each side circuit at the points 1G and 17, to aid in reducing side circuit transmission losses in the series windings of the autotransformers by acting as a short circuit thereon at telephone frequencies. As before, the autotransformer windings are best assembled upon a single core, as illustrated in Fig. 6, with the ele ments belonging to each side circuit on separate halves. As the pairs of series windings, like the bridge windings, are practically free from side circuit current, they may also conveniently be carried through a twisted pair. For a circuit in which the open wire phantom presentsan impedance of 1400 ohms, while the terminal cable has an impedance of 90() ohms, a coil with windings as follows might be employed: Each bridge winding lw2 or w3, 1117 turns of No. 26 B. & S. gage singIe"`cotton-covered copper wire with a direct currentV resistance of ohms and an impedance value together in series-parallelaiding of 3535 ohms and 4.5 henries; series windings w, w, each 280 turns of No. Q0 B. & S. gage single cotton-covered copper wire, direct current resistance of 2.5 ohms.. impedance together in series-parallelen ng 222 ohms and 0.28 of a henry. impedance between the bridge and cries groups would be 885 ohms and 1.12 lien rfwo microfarad condensers c and c n: be used, while the condenser 02 would be one microfarad or less.

Having thus described. our invertion.I we claim:

1. In a telephone circuit comprising circuits together furnishing a phan cuit and physical extensions of sait cuits and phantom circuit, a phanto ing device connecting each side circor its extension anfrom which the piiamifm als The mutual through the phantom-forming devices to connect the respective sections of the' conductors of the side circuits.

2. In a telephone circuit comprising side circuits together furnishing a phantom circuit and physical extensions-of said side circuits and phantom circuit, a.v phantom-forming device connecting each side circuit and 'its extension and from whichthe phantom extension is led, and an autotransformer furnishing direct current paths -through the phantom-forming device to connect the respective sections of the` conductors of the side circuits. 4

3. In a telephone circuit co circuits together furnishing'a p antom circuit and physical extensions of said side circuits and phantom circuit, a phantom-forming device connecting each side circuit and its extension and from which the phantom extension is led, and an autotransformer having windings in series with the side circuits and the extensions.

4. A phantom circuit comprising side circuits and extensions thereof, phantom-form-l i, rising side ing devices inductively associating the side circuits and their extensions, conductive connections between said side circuits and their extensions, and means associated with said conductive connections to prevent the transfer of crosstalk and noise currents between the phantom circuit and side circuit extensions.

5. In a telephone circuit comprising side circuits together furnishing a phantom cir-` cuit and physical extensions of said side circuits and phantom circuit, a phantom-forming device connecting each side circuit and its extension and from which the phantom extension is led, means furnishing direct current paths through the phantom-forming device to connect the respective sections of the conductoi's of the side circuits, and means associated with said connecting means for preventing disturbances in the circuit extensions resulting from the establishment of the directcurrent paths.

6. A phantom circuit comprising side circuits and extensions thereof, phantom-forming devices inductively associating the side circuits with their extensions, conductive connections between said side circuits and their extensions, impedance included in said connections, and a bridge between the side circuit extensions at the phantom-forming devices. 4

7. In a telephone circuit comprising side circuits together furnishing a phantom circuit and physical extensions of said side circuits and phantom circuit, and a reflectionreducing dcvice interposed between the phantom circuit and its physical extension and serving to prevent the transfer of disturbing current between the phantom circuit and the side circuit extensions.

8. In a telephone circuit comprising side `of a phantom circuit, said side circuit circuits together furnishing a phantom circuit and physical extensions of said side circuits and phantom circuit, and an autotransformer interposed between the phantom circuit and its physical extension and having windings in series with the side circuit extensions.

9. 'lhe combination with the side circuit of-a phantom circuit, said side circuit being provided withl a terminal extension, of a phantom-forming device' having line windings and extension windings, and a connecting device with windingsjcining said line and extension windings.`

10. The combination with the side circuit being provided with 4a .terminal extension, of a phantom-forming device having line vwindings and extension windinvs, and a ktransformer provided with win `ngs connecting said line and extension windings.

11. The combination with two line circuits, of means for connecting said line circuits and forming a phantom circuit 'therefrom, physlcal extensions from the lmecircuits and phantom circuit, and a bridge be- Ytween the line extensions at the connecting means. f

12. The combination with two line circuits, of means for connecting said line circuits and forming a phantom circuit therefrom, physical extensions from the line circu1ts and phantom circuit, and abridge between the line ,extensions at the neutralv points therein.

13. The combination with two line circuits, of means for, connecting said line circuits and forming'a phantom circuit therefrom, physical extensions from the line circuits and phantom circuit` a bridge across each line extension, condensers in the bridges, and a short circuit between the line extensions from points between the condensers.

14. The combination with two line circuits, of means for connecting said line circuits and forming a phantom circuit therefrom, physical extensions from the line c1rcults and phantom circuits, and an autotransformer connecting each line circuitr aimeras 17. Twophysical circuits and extensions thereof, a phantomA repeating coil associating the sections of each circuit, a phantom circuit extension of diiierent impedance from the phantom furnished by the two physical circuits, and an autotransformer having windings in the phantom and its extension and joining the sections of the physical circuits.

18. Two physical circuits and extensions thereof, a phantom.. repeating coil associat` ing the sections of each circuit, a phantom circuit extension of different impedance from the phantom furnished by the two physical circuits, and an autotransorme-r haring windings in the phantompand its extension and joining the ysections of the vphysical circuits, the windings for the phantom being in a bridge of said phantom.

19. Two physical circuits and extensions thereof, a phantom repeating coil associating the sections of each circuit, a phantom circuit extension of different impedance from the phantom furnished by the two physical circuits, an Vautotransformer having windings in the phantom and its exten- 'sionarid joining the sections of the physical circuits, a bridge across each line circuit, and a condenser in the bridge.

20. Two 'physical circuits and extensions thereof,'a phantom repeating coil associating the sections of each circuit, a phantom circuit extension of different impedance from the phantom furnished by the two physical circuits, an autotransformer having windings in the phantom and its extencuits, an autotransformer having windings.

in the phantom and its extension and joining the sections of the physical circuits, the windings for the phantom being in a bridge of said phantom, balanced condensers ineluded in'each' bridge with the autotransformer windings, and .a short circuit connecting the bridges from points between the balanced condensers.

In testimony whereof We -have signed our names to this specification in the'presence of two subscribing witnesses, this 21th day of September, 1914.

FRANK' H. FAY. THOMAS SHAW. Vitnesses:

LLOYD ESPENSCHIED, "WALTER J. Donor-1.v In testimony whereof I have vsigned my name to this specification in the presence of 'two subscribing Witnesses, this i28th day of September, 1914.V

y JAMESv J. PILLIOD. Witnesses: Y l

E. J. BsNzrNo,

H. S. FoLAND.

Copies ot thlspatent may be obtained for tve'cents eacli, by addressing the Commissioner of Patents, 'Washington,-D. C. 

